U.S. patent application number 13/383411 was filed with the patent office on 2012-05-10 for electrochemical device.
This patent application is currently assigned to TAIYO YUDEN CO., LTD.. Invention is credited to Tomofumi Akiba, Naoto Hagiwara, Katsuei Ishida, Satoshi Nagura, Shin Nakagawa, Tomohiro Taguchi, Toshiya Terui.
Application Number | 20120113566 13/383411 |
Document ID | / |
Family ID | 43449233 |
Filed Date | 2012-05-10 |
United States Patent
Application |
20120113566 |
Kind Code |
A1 |
Terui; Toshiya ; et
al. |
May 10, 2012 |
ELECTROCHEMICAL DEVICE
Abstract
Provided is an electrochemical device which is capable of
suppressing problems affecting the capacitor element as a whole,
such as a drop in its voltage resistance characteristics and
shortening of its life. The capacitor element (10) is constituted
of a laminate formed by superposition of a first electrode sheet
(11), a separation sheet (14), a second electrode sheet (12), a
separation sheet (14), and a third electrode sheet (13) in the
named order from the bottom, and folding the laminate along a
reference line VSL to double the laminate. In the resulting folded
laminate, a collector electrode layer (11a) and polarizable
electrode layer (11b) of the first electrode sheet (11), the
collector electrode layer (12a) and polarizable electrode layer
(12b) of the second electrode sheet (12), the collector electrode
(13a) and polarizable electrode layer (13b) of the third electrode
sheet (13), and the two separation sheets (14) are connected to
each other at the respective folded locations.
Inventors: |
Terui; Toshiya; (Gunma,
JP) ; Akiba; Tomofumi; (Gunma, JP) ; Ishida;
Katsuei; (Gunma, JP) ; Hagiwara; Naoto;
(Gunma, JP) ; Nagura; Satoshi; (Nagano, JP)
; Nakagawa; Shin; (Nagano, JP) ; Taguchi;
Tomohiro; (Nagano, JP) |
Assignee: |
TAIYO YUDEN CO., LTD.
Taito-ku, Tokyo
JP
|
Family ID: |
43449233 |
Appl. No.: |
13/383411 |
Filed: |
June 3, 2010 |
PCT Filed: |
June 3, 2010 |
PCT NO: |
PCT/JP2010/059410 |
371 Date: |
January 10, 2012 |
Current U.S.
Class: |
361/502 |
Current CPC
Class: |
Y02E 60/13 20130101;
H01G 11/70 20130101; H01G 11/66 20130101; H01G 11/52 20130101; H01G
9/02 20130101; H01G 11/28 20130101; H01M 10/058 20130101; H01M
10/04 20130101; H01G 11/74 20130101; H01M 10/052 20130101; H01G
11/22 20130101; Y02E 60/10 20130101 |
Class at
Publication: |
361/502 |
International
Class: |
H01G 9/155 20060101
H01G009/155 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 17, 2009 |
JP |
2009-169290 |
Mar 29, 2010 |
JP |
2010-075347 |
Claims
1. An electrochemical device having a structure wherein a capacitor
element is sealed in a package, said capacitor element having a
configuration in which two or more electrode sheets, each having a
collector electrode layer and a polarizable electrode layer formed
on at least one side of the collector electrode layer, are stacked
to form a laminate with a separation sheet inserted between the
polarizable electrode layers of adjacent different electrode
sheets, said laminate being folded along a reference line, to be
superposed, wherein each of the collector electrode layer and
polarizable electrode layer constituting each electrode sheet, and
the separation sheet, is continuous through the respective folded
locations.
2. An electrochemical device according to claim 1, wherein, of the
two or more electrode sheets, provided on both ends of the
collector electrode layer of the electrode sheet having one
polarity are lead connection parts that face each other in the
aforementioned configuration and these lead connection parts are
interconnected; and provided on both ends of the collector
electrode layer of the electrode sheet having the opposite polarity
are lead connection parts that face each other at positions not
contacting the lead connection parts of the aforementioned
electrode sheet in the aforementioned configuration and these lead
connection parts are interconnected.
3. An electrochemical device according to claim 2, wherein the lead
connection parts of the electrode sheet having the one polarity are
interconnected via the separation sheet, and the lead connection
parts of the electrode sheet having the opposite polarity are
interconnected via the separation sheet.
4. An electrochemical device according to claim 1, wherein the
laminate comprises: as the two or more electrode sheets, a first
electrode sheet having a collector electrode layer and a
polarizable electrode layer formed on one side of the collector
electrode layer; a second electrode sheet having a collector
electrode layer and polarizable electrode layers formed on both
sides of the collector electrode layer; a third electrode layer
having a collector electrode layer and a polarizable electrode
layer formed on the other side of the collector electrode layer;
and as the separation sheet, two separation sheets; wherein, of the
two separation sheets, one separation sheet is present between the
polarizable electrode layer of the first electrode sheet and one
polarizable electrode layer of the second electrode sheet, and the
other separation sheet is present between the other polarizable
electrode layer of the second electrode sheet and the polarizable
electrode layer of the third electrode sheet.
5. An electrochemical device according to claim 1, wherein the
laminate comprises: as the two or more electrode sheets, a first
electrode sheet having a collector electrode layer and a
polarizable electrode layer formed on one side of the collector
electrode layer; a second electrode sheet having a collector
electrode layer and a polarizable electrode layer formed on another
side of the collector electrode layer; and as the separation sheet,
a separation sheet; wherein the separation sheet is present between
the polarizable electrode layer of the first electrode sheet and
the polarizable electrode layer of the second electrode sheet.
6. An electrochemical device according to claim 1, wherein, of the
two or more electrode sheets, at least one electrode sheet having
one polarity is such that its collector electrode layer has
anti-displacement projections on its outer periphery, which
anti-displacement projections extend from the outer periphery
beyond the adjacent polarizable electrode layer and bite into the
adjacent separation sheet without piercing therethrough, and at
least one electrode sheet having the opposite polarity is such that
its collector electrode layer has anti-displacement projections on
its outer periphery, which anti-displacement projections extend
from the outer periphery beyond the adjacent polarizable electrode
layer and bite into the adjacent separation sheet without piercing
therethrough.
7. An electrochemical device according to claim 2, wherein the
laminate comprises: as the two or more electrode sheets, a first
electrode sheet having a collector electrode layer and a
polarizable electrode layer formed on one side of the collector
electrode layer; a second electrode sheet having a collector
electrode layer and polarizable electrode layers formed on both
sides of the collector electrode layer; a third electrode layer
having a collector electrode layer and a polarizable electrode
layer formed on the other side of the collector electrode layer;
and as the separation sheet, two separation sheets; wherein, of the
two separation sheets, one separation sheet is present between the
polarizable electrode layer of the first electrode sheet and one
polarizable electrode layer of the second electrode sheet, and the
other separation sheet is present between the other polarizable
electrode layer of the second electrode sheet and the polarizable
electrode layer of the third electrode sheet.
8. An electrochemical device according to claim 3, wherein the
laminate comprises: as the two or more electrode sheets, a first
electrode sheet having a collector electrode layer and a
polarizable electrode layer formed on one side of the collector
electrode layer; a second electrode sheet having a collector
electrode layer and polarizable electrode layers formed on both
sides of the collector electrode layer; a third electrode layer
having a collector electrode layer and a polarizable electrode
layer formed on the other side of the collector electrode layer;
and as the separation sheet, two separation sheets; wherein, of the
two separation sheets, one separation sheet is present between the
polarizable electrode layer of the first electrode sheet and one
polarizable electrode layer of the second electrode sheet, and the
other separation sheet is present between the other polarizable
electrode layer of the second electrode sheet and the polarizable
electrode layer of the third electrode sheet.
9. An electrochemical device according to claim 2, wherein the
laminate comprises: as the two or more electrode sheets, a first
electrode sheet having a collector electrode layer and a
polarizable electrode layer formed on one side of the collector
electrode layer; a second electrode sheet having a collector
electrode layer and a polarizable electrode layer formed on another
side of the collector electrode layer; and as the separation sheet,
a separation sheet; wherein the separation sheet is present between
the polarizable electrode layer of the first electrode sheet and
the polarizable electrode layer of the second electrode sheet.
10. An electrochemical device according to claim 3, wherein the
laminate comprises: as the two or more electrode sheets, a first
electrode sheet having a collector electrode layer and a
polarizable electrode layer formed on one side of the collector
electrode layer; a second electrode sheet having a collector
electrode layer and a polarizable electrode layer formed on another
side of the collector electrode layer; and as the separation sheet,
a separation sheet; wherein the separation sheet is present between
the polarizable electrode layer of the first electrode sheet and
the polarizable electrode layer of the second electrode sheet.
11. An electrochemical device according to claim 2, wherein, of the
two or more electrode sheets, at least one electrode sheet having
one polarity is such that its collector electrode layer has
anti-displacement projections on its outer periphery, which
anti-displacement projections extend from the outer periphery
beyond the adjacent polarizable electrode layer and bite into the
adjacent separation sheet without piercing therethrough, and at
least one electrode sheet having the opposite polarity is such that
its collector electrode layer has anti-displacement projections on
its outer periphery, which anti-displacement projections extend
from the outer periphery beyond the adjacent polarizable electrode
layer and bite into the adjacent separation sheet without piercing
therethrough.
12. An electrochemical device according to claim 3, wherein, of the
two or more electrode sheets, at least one electrode sheet having
one polarity is such that its collector electrode layer has
anti-displacement projections on its outer periphery, which
anti-displacement projections extend from the outer periphery
beyond the adjacent polarizable electrode layer and bite into the
adjacent separation sheet without piercing therethrough, and at
least one electrode sheet having the opposite polarity is such that
its collector electrode layer has anti-displacement projections on
its outer periphery, which anti-displacement projections extend
from the outer periphery beyond the adjacent polarizable electrode
layer and bite into the adjacent separation sheet without piercing
therethrough.
Description
TECHNICAL FIELD
[0001] The present invention relates to an electrochemical device
structured in such a way that a capacitor element is sealed in a
package.
PRIOR ART
[0002] A capacitor element used in an electric double-layer
capacitor, which is a representative example of this type of
electrochemical device, generally has a layer structure constituted
by a collector electrode layer, a polarizable electrode layer, a
separation sheet, a polarizable electrode layer, a collector
electrode layer, . . . , a collector electrode layer, a polarizable
electrode layer, a separation sheet, a polarizable electrode layer,
and a collector electrode layer stacked on top of each other in
this order (refer to Patent Literature 1). In other words, a set of
collector electrode layer, polarizable electrode layer, separation
sheet, polarizable electrode layer and collector electrode layer
constitutes one charge/discharge cell, meaning that such capacitor
element can be expressed by an equivalent circuit where multiple
charge/discharge cells are electrically connected in parallel with
a pair of leads.
[0003] With such an electric double-layer capacitor, applying
voltage to the capacitor element generates an electric field
according to the voltage, and lines of electric force generate
according to the electric field. These lines of electric force
gather at the edges of each polarizable electrode layer, so the
density of lines of electric force at each of these edges becomes
higher than in other locations. Also because lines of electric
force are directed from the positive electrode toward the negative
electrode, in a situation where, for example, a polarizable
electrode layer on the positive electrode side is positioned at the
outermost point and a polarizable electrode layer on the negative
electrode side is positioned on the inside of the former, the
highest density of lines of electric force appears at the edges of
these polarizable electrode layers.
[0004] In other words, a capacitor element having the
aforementioned layer structure is vulnerable to breakage and other
damage due to high density of lines of electric force at the edges
of each polarizable electrode layer, and because of this damage it
presents the risk of problems affecting the capacitor element as a
whole, such as a drop in its voltage resistance characteristics and
shortening of its life.
[0005] Patent Literature 2 discloses a capacitor element for an
electric double-layer capacitor having a collector electrode layer
folded into the shape of the letter U, but since the two
polarizable electrode layers formed in the collector electrode
layer are separate, it is still difficult to avoid the
aforementioned problems even when this capacitor element is
used.
[0006] Although specific explanation is omitted, it goes without
saying that problems similar to those mentioned above also affect
lithium ion capacitors, redox capacitors, lithium ion batteries and
other electrochemical devices having a capacitor element whose
structure is roughly the same as the aforementioned capacitor
element for an electric double-layer capacitor.
PRIOR ART LITERATURES
Patent Literatures
[0007] Patent Literature 1: Japanese Patent Laid-open No.
2002-015954 [0008] Patent Literature 2: Japanese Patent Laid-open
No. Hei 08-064479
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0009] The object of the present invention is to provide an
electrochemical device capable of reliably suppressing problems
affecting the capacitor element as a whole, such as a drop in its
voltage resistance characteristics and shortening of its life.
Means for Solving the Problems
[0010] To achieve the aforementioned object, the present invention
provides an electrochemical device having a structure wherein a
capacitor element is sealed in a package, said capacitor element
having a configuration in which two or more electrode sheets, each
having a collector electrode layer and a polarizable electrode
layer formed on at least one side of the collector electrode layer,
are stacked on top of each other to form a laminate with a
separation sheet inserted between the polarizable electrode layers,
said laminate being folded along a reference line, to be
superposed, wherein each of the collector electrode layer and
polarizable electrode layer constituting each electrode sheet, and
the separation sheet, is continuous through the respective folded
locations.
[0011] According to this electrochemical device, the capacitor
element has a configuration in which stacked layers are folded
along the reference line and superposed, while the collector
electrode layer and polarizable electrode layer constituting each
electrode sheet, and the separation sheet, are connected to each
other at the respective folded locations, and therefore even though
the layer structure in section view is the same as that of the
conventional capacitor element, the edge areas in each polarizable
electrode layer can be reduced compared to the conventional
capacitor element.
[0012] In other words, while the conventional capacitor element is
vulnerable to breakage and other damage due to higher density of
lines of electric force at the edges of each polarizable electrode
layer when voltage is applied to the capacitor element, and
therefore presents the risk of problems affecting the capacitor
element as a whole, such as a drop in its voltage resistance
characteristics and shortening of its life caused by the damage,
the aforementioned capacitor element has fewer edge areas in each
polarizable electrode layer compared to the conventional capacitor
element and can therefore effectively suppress the aforementioned
damage and reliably suppress problems affecting the capacitor
element as a whole, such as a drop in its voltage resistance
characteristics and shortening of its life caused by such
damage.
Effects of the Invention
[0013] According to the present invention, an electrochemical
device capable of suppressing problems affecting the capacitor
element as a whole, such as a drop in its voltage resistance
characteristics and shortening of its life, can be provided.
[0014] The aforementioned object and other objects,
constitution/features and operation/effects of the present
invention are revealed by the explanations given below as well as
the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 (A) is a top view of an electric double-layer
capacitor to which the present invention is applied, FIG. 1 (B) is
a left side view of the same, and FIG. 1 (C) is a front view of the
same.
[0016] FIG. 2 (A) is a top view of a first electrode sheet, while
FIG. 2 (B) is a left side view of the same.
[0017] FIG. 3 (A) is a top view of a second electrode sheet, while
FIG. 3 (B) is a left side view of the same.
[0018] FIG. 4 (A) is a top view of a third electrode sheet, while
FIG. 4 (B) is a left side view of the same.
[0019] FIG. 5 (A) is a top view of a separation sheet, while FIG. 5
(B) is a left side view of the same.
[0020] FIGS. 6 (A) to (D) are drawings showing a method for
creating a first electrode sheet, second electrode sheet, third
electrode sheet and separation sheet.
[0021] FIG. 7 (A) is a top view of a first electrode sheet, second
electrode sheet, third electrode sheet and separation sheet stacked
on top of each other to form a laminate, while FIG. 7 (B) is a left
side view of the same.
[0022] FIG. 8 (A) is a top view showing the laminate in FIG. 7 (A)
being folded and superposed, while FIG. 8 (B) is an enlarged left
side view of the same.
[0023] FIG. 9 (A) is a top view of lead connection parts of the
folded laminate in FIG. 8 (A), FIG. 9 (B) is an enlarged left side
view of the same, and FIG. 9 (C) is an enlarged section view of
FIG. 9 (B) cut along line S1-S1.
[0024] FIG. 10 (A) is a top view showing the capacitor element in
FIG. 9 (A) to which leads are connected, while FIG. 10 (B) is a
left side view of the same.
[0025] FIG. 11 (A) is a top view of a package sheet, FIG. 11 (B) is
a left side view of the same, and FIG. 11 (C) is an enlarged
section view of X1 in FIG. 11 (B).
[0026] FIG. 12 is a top view showing a capacitor element inserted
in a concaved part of a package sheet.
[0027] FIG. 13 is a top view showing a package sheet being folded
and superposed.
[0028] FIG. 14 is a top view showing the semi-finished package in
FIG. 13 whose left side and right side are heat-sealed.
[0029] FIG. 15 is a top view showing the semi-finished package in
FIG. 14 whose front side is heat-sealed.
[0030] FIGS. 16 (A) and (B) are enlarged section views
corresponding to FIG. 9 (C), showing examples of anti-displacement
projections provided on collector electrode layers of electrode
sheets.
[0031] FIG. 17 (A) is a top view of a lithium ion capacitor to
which the present invention is applied, FIG. 17 (B) is a left side
view of the same, and FIG. 17 (C) is a front view of the same.
[0032] FIG. 18 (A) is a top view of a first electrode sheet, while
FIG. 18 (B) is a left side view of the same.
[0033] FIG. 19 (A) is a top view of a second electrode sheet, while
FIG. 19 (B) is a left side view of the same.
[0034] FIG. 20 (A) is a top view of a separation sheet, while FIG.
20 (B) is a left side view of the same.
[0035] FIGS. 21 (A) to (C) are drawings showing a method for
creating a first electrode sheet, second electrode sheet and
separation sheet.
[0036] FIG. 22 (A) is a top view of a first electrode sheet, second
electrode sheet and separation sheet stacked on top of each other
to form a laminate, while FIG. 22 (B) is a left side view of the
same.
[0037] FIG. 23 (A) is a top view showing the laminate in FIG. 22
(A) being folded and superposed, while FIG. 23 (B) is an enlarged
left side view of the same.
[0038] FIG. 24 (A) is a top view of lead connection parts of the
folded laminate in FIG. 23 (A), FIG. 24 (B) is an enlarged left
side view of the same, and FIG. 24 (C) is an enlarged section view
of FIG. 24 (B) cut along line S2-S2.
[0039] FIG. 25 (A) is a top view showing the capacitor element in
FIG. 24 (A) to which leads are connected, while FIG. 25 (B) is a
left side view of the same.
[0040] FIG. 26 (A) is a top view of a package sheet, FIG. 26 (B) is
a left side view of the same, and FIG. 26 (C) is an enlarged
section view of X2 in FIG. 26 (B).
[0041] FIG. 27 is a top view showing a capacitor element inserted
in a concaved part of a package sheet.
[0042] FIG. 28 is a top view showing a package sheet being folded
and superposed.
[0043] FIG. 29 is a top view showing the semi-finished package in
FIG. 28 whose right side and front side are heat-sealed.
[0044] FIG. 30 is a top view showing the semi-finished package in
FIG. 29 whose left side is heat-sealed.
MODE FOR CARRYING OUT THE INVENTION
First Embodiment
[0045] FIGS. 1 to 15 show an embodiment where the present invention
is applied to an electric double-layer capacitor. This electric
double-layer capacitor has a capacitor element 10, a pair of leads
20 connected to the capacitor element 10, and a package 30 in which
the capacitor element 10 is sealed in a manner partially exposing
the pair of leads 20.
[0046] Note that, in the following explanations, the direction
toward the viewer, away from the viewer, right, left, bottom and
top in FIG. 1 (A) are referred to as top, bottom, front, rear, left
and right, respectively, while the corresponding directions in
other drawings are also referred to as top, bottom, front, rear,
left and right, respectively, for the convenience of
explanation.
[0047] First, FIGS. 2 to 9 are used to explain the constitution of,
and method for creating, the capacitor element 10.
[0048] To create the capacitor element 10, a first electrode sheet
11 shown in FIGS. 2 (A) and (B), a second electrode sheet 12 shown
in FIGS. 3 (A) and (B), a third electrode sheet 13 shown in FIGS. 4
(A) and (B), and a separation sheet 14 shown in FIGS. 5 (A) and (B)
are prepared.
[0049] As shown in FIGS. 2 (A) and (B), the first electrode sheet
11 has a rectangular collector electrode layer 11a of specified
longitudinal dimension L11 and lateral dimension W11, as well as a
polarizable electrode layer 11b formed over the entire top surface
of the collector electrode layer 11a by means of coating, etc.
(note that, in the drawings, the front edge and rear edge of the
polarizable electrode layer 11b are slightly overlapping each lead
connection part 11a1). The collector electrode layer 11a is made of
aluminum, platinum or other conductive material, and its thickness
is 5 to 50 .mu.m. The polarizable electrode layer 11b is made of
PAS (polyacene-based organic semiconductor), active carbon or other
active material, and its thickness is 10 to 50 .mu.m. Also, a
rectangular lead connection part 11a1 is provided on the right side
of the collector electrode layer 11a on both ends in the
longitudinal direction in a manner integral with, and at the same
thickness as, the collector electrode layer 11a.
[0050] As shown in FIGS. 3 (A) and (B), the second electrode sheet
12 has a rectangular collector electrode layer 12a of longitudinal
dimension L12 identical to longitudinal dimension L11 mentioned
above, and lateral dimension W12 identical to lateral dimension W11
mentioned above, as well as polarizable electrode layers 12b formed
over the entire top surface and entire bottom surface of the
collector electrode layer 12a by means of coating, etc. (note that,
in the drawings, the front edge and rear edge of the polarizable
electrode layer 12b are slightly overlapping each lead connection
part 12a1). The material and thickness of the collector electrode
layer 12a are the same as those of the aforementioned collector
electrode layer 11a, while the material and thickness of each
polarizable electrode layer 12b are the same as those of the
aforementioned polarizable electrode layer 11b. Also, a lead
connection part 12a1 having the same shape as the aforementioned
lead connection part 11a1 is provided on the left side of the
collector electrode layer 12a on both ends in the longitudinal
direction in a manner integral with, and at the same thickness as,
the collector electrode layer 12a.
[0051] As shown in FIGS. 4 (A) and (B), the third electrode sheet
13 has a rectangular collector electrode layer 13a of longitudinal
dimension L13 identical to longitudinal dimension L11 mentioned
above, and lateral dimension W13 identical to lateral dimension W11
mentioned above, as well as a polarizable electrode layer 13b
formed over the entire bottom surface of the collector electrode
layer 13a by means of coating, etc. (note that, in the drawings,
the front edge and rear edge of the polarizable electrode layer 13b
are slightly overlapping each lead connection part 13a1). The
material and thickness of the collector electrode layer 13a are the
same as those of the aforementioned collector electrode layer 11a,
while the material and thickness of each polarizable electrode
layer 13b are the same as those of the aforementioned polarizable
electrode layer 11b. Also, a lead connection part 13a1 having the
same shape as the aforementioned lead connection part 11a1 is
provided on the right side of the collector electrode layer 13a on
both ends in the longitudinal direction at the same position as the
aforementioned lead connection part 11a1, in a manner integral
with, and at the same thickness as, the collector electrode layer
13a.
[0052] In other words, the shape in top view of the collector
electrode layer 11a (excluding the lead connection part 11a1) of
the first electrode sheet 11, shape in top view of the collector
electrode layer 12a (excluding the lead connection part 12a1) of
the second electrode sheet 12, and shape in top view of the
collector electrode layer 13a (excluding the lead connection part
13a1) of the third electrode sheet 13, are identical.
[0053] Also, the shape in top view of the polarizable electrode
layer 11b of the first electrode sheet 11 and shape in bottom view
of the polarizable electrode layer 12b on the bottom surface of the
second electrode sheet 12 are identical. The shape in top view of
the polarizable electrode layer 12b on the top surface of the
second electrode sheet 12 and shape in bottom view of the
polarizable electrode layer 13b of the third electrode sheet 13 are
identical. As shown by the drawings, the polarizable electrode
layer 12b on the top surface of the second electrode sheet 12 and
polarizable electrode layer 13b of the third electrode sheet 13
have 180-degree reversed shapes of the polarizable electrode layer
11b of the first electrode sheet 11 in the lateral direction or
longitudinal direction, respectively.
[0054] Furthermore, the collector electrode layer 11a (including
the lead connection part 11a1) and polarizable electrode layer 11b
of the first electrode sheet 11 are linearly symmetrical over the
reference line VSL running at the center in the longitudinal
direction as shown in FIG. 2 (A). The collector electrode layer 12a
(including the lead connection part 12a1) and each polarizable
electrode layer 12b of the second electrode sheet 12 are linearly
symmetrical over the reference line VSL running at the center in
the longitudinal direction as shown in FIG. 3 (A). The collector
electrode layer 13a (including the lead connection part 13a1) and
polarizable electrode layer 13b of the third electrode sheet 13 are
linearly symmetrical over the reference line VSL running at the
center in the longitudinal direction as shown in FIG. 4 (A).
[0055] As shown in FIGS. 5 (A) and (B), the separation sheet 14 has
a rectangular shape of longitudinal dimension L14 slightly larger
than longitudinal dimension L11 mentioned above, and lateral
dimension W14 slightly larger than lateral dimension W11 mentioned
above. The separation sheet 14 is made of cellulose sheet, plastic
sheet or other ion permeation sheet, and its thickness is approx.
10 to 50 .mu.m.
[0056] The aforementioned first electrode sheet 11, second
electrode sheet 12, third electrode sheet 13 and separation sheet
14 can be obtained easily by cutting material sheets BS1 to BS4
along virtual lines PL1 to PL4 and then punching out the insides,
respectively, as shown in FIGS. 6 (A) to (D). As shown by the
drawings, the material sheet BS1 for first electrode sheet 11 is a
strip-shaped collector electrode layer with a strip-shaped
polarizable electrode layer formed on its top surface, the material
sheet BS2 for second electrode sheet 12 is a strip-shaped collector
electrode layer with a strip-shaped polarizable electrode layer
formed on its top surface and bottom surface, and the material
sheet BS3 for third electrode sheet 13 is a strip-shaped collector
electrode layer with a strip-shaped polarizable electrode layer
formed on its bottom surface.
[0057] To create the capacitor element 10 (refer to FIGS. 9 (A) and
1 (A)), the prepared first electrode sheet 11, second electrode
sheet 12, third electrode sheet 13 and two separation sheets 14 are
stacked in such a way that they are ordered as first electrode
sheet 11, separation sheet 14, second electrode sheet 12,
separation sheet 14 and third electrode sheet 13 from the bottom,
as shown in FIGS. 7 (A) and (B).
[0058] When stacking the sheets, the outer peripheries of the
collector electrode layers 11a, 12a, 13a of the first electrode
sheet 11, second electrode sheet 12 and third electrode sheet 13
are caused to align in the stacking direction, while the outer
peripheries of the lead connection parts 11a1, 13a1 of the first
electrode sheet 11 and third electrode sheet 13 are caused to align
in the stacking direction. Also, the outer peripheries of the two
separation sheets 14 are caused to project outward from the outer
peripheries of the respective collector electrode layers 11a, 12a,
13a, while the outer peripheries of the respective separation
sheets 14 are caused to align in the stacking direction.
Furthermore, the lead connection parts 11a1, 12a1, 13a1 of the
first electrode sheet 11, second electrode sheet 12 and third
electrode sheet 13 are caused to project by the same length from
each separation sheet 14.
[0059] This way, a laminate (no reference numeral) is obtained
where the polarizable electrode layer 11b of the first electrode
sheet 11 and bottom polarizable electrode layer 12b of the second
electrode sheet 12 are contacting the bottom separation sheet 14,
while the top polarizable electrode layer 12b of the second
electrode sheet 12 and polarizable electrode layer 13b of the third
electrode sheet 13 are contacting the top separation sheet 14.
[0060] Next, as shown in FIGS. 8 (A) and (B), the part of the
laminate in FIG. 7 (A) on the left side of the center in the
longitudinal direction is folded upward along the reference line
VSL shown in the drawing, and the left side is superposed with the
right side.
[0061] At the time of this superposition, the outer peripheries of
the lead connection parts 11a1, 13a1 of the first electrode sheet
11 and third electrode sheet 13 are caused to align in the
superposing direction, while the outer peripheries of the lead
connection parts 12a1 of the second electrode sheet 12 are caused
to align in the superposing direction.
[0062] This way, a folded laminate (no reference numeral) is
obtained, which has a configuration in which the first electrode
sheet 11, second electrode sheet 12, third electrode sheet 13 and
two separation sheets 14 are folded into two at an angle of approx.
180 degrees over the reference line VSL in such a way that the lead
connection parts 11a1 of the first electrode sheet 11 are facing
the lead connection parts 13a1 of the third electrode sheet 13, and
the lead connection parts 12a1 of the second electrode sheet 12 are
facing each other.
[0063] The next step on this folded laminate shown in FIG. 8 (A) is
that, as shown in FIGS. 9 (A) to (C) the mutually facing lead
connection parts 11a1 of the first electrode sheet 11 and lead
connection parts 13a1 of the third electrode sheet 13 are
superposed and two locations on both sides in the lateral direction
are directly joined by means of spot-welding, ultrasonic welding,
clinching, etc., to interconnect the lead connection parts 11a1,
13a1 (refer to the joining location WP1). Also, the mutually facing
lead connection parts 12a1 of the second electrode sheet 12 are
superposed at positions not contacting the aforementioned lead
connection parts 11a1, 13a1, and two locations on both sides in the
lateral direction are directly joined by means of spot-welding,
ultrasonic welding, clinching, etc., to interconnect the lead
connection parts 12a1 (refer to the joining location WP1).
[0064] This way, the capacitor element 10 is obtained, which has a
configuration in which the first electrode sheet 11, second
electrode sheet 12, third electrode sheet 13 and two separation
sheets 14 are folded into two at an angle of approx. 180 degrees
over the reference line VSL, while the lead connection parts 11a1
of the first electrode sheet 11 and lead connection parts 13a1 of
the third electrode sheet 13 are interconnected, and the lead
connection parts 12a1 of the second electrode sheet 12 are
interconnected.
[0065] It should be noted that in FIGS. 2 to 9 (and also in FIG.
10), the thickness of the collector electrode layer 11a and
polarizable electrode layer 11b of the first electrode sheet 11,
the thickness of the collector electrode layer 12a and each
polarizable electrode layer 12b of the second electrode sheet 12,
the thickness of the collector electrode layer 13a and polarizable
electrode layer 13b of the third electrode sheet 13, and the
thickness of the separation sheet 14, have been increased from
their actual thicknesses for the convenience of illustration, and
therefore the vertical dimensions (overall thicknesses) in FIGS. 7
(B), 8 (B), 9 (B) and 9 (C) appear thicker than they actually
are.
[0066] However, the thickness of the collector electrode layer 11a
and polarizable electrode layer 11b of the first electrode sheet
11, the thickness of the collector electrode layer 12a and each
polarizable electrode layer 12b of the second electrode sheet 12,
the thickness of the collector electrode layer 13a and polarizable
electrode layer 13b of the third electrode sheet 13, and the
thickness of the separation sheet 14, are in a range of 5 to 50
.mu.m and therefore even when the average of all layers is assumed
as 30 .mu.m, for example, the actual vertical dimension (overall
thickness) in FIG. 7 (B) becomes 270 .mu.m, while the actual
vertical dimension (overall thickness) in FIGS. 8 (B), 9 (B) and 9
(C) becomes 540 .mu.m.
[0067] In other words, the actual vertical dimension (overall
thickness) of the capacitor element 10 shown in FIG. 9 (A) is less
than 1000 .mu.m, meaning that, with the folded laminate in FIG. 9
(B), the radius of curvature of the outer surface at the folded
location is much smaller than illustrated and consequently the lead
connection parts 11a1, 12a1, 13a1 are virtually not displaced in
the longitudinal direction when folded. In addition, the
polarizable electrode layers 11b, 12b, 13b do not separate from the
collector electrode layers 11a, 12a, 13a when the laminate is
folded, and the polarizable electrode layers 11b, 12b, 13b do not
lose contact with each separation sheet 14, either. Furthermore,
the collector electrode layers 11a, 12a, 13a, polarizable electrode
layers 11b, 12b, 13b and each separation sheet 14 have sufficient
flexibility to permit folding and thus do not break at the folded
locations.
[0068] Also in FIG. 9 (B), the lead connection parts are partially
extended for the convenience of illustration, or specifically to
explain the connection of lead connection parts 11a1, 13a1 and the
connection of lead connection parts 12a1 on the folded laminate. As
understood from the foregoing explanation, however, in reality the
lead connection parts can be connected without such extensions.
[0069] Next, FIG. 10 is used to explain the constitution of the
lead 20 and how it is connected to the capacitor element 10.
[0070] To connect the lead 20 to the capacitor element 10, the lead
20 shown in FIGS. 10 (A) and (B) is prepared. This lead 20 is
formed into a short strip shape made of aluminum, platinum, copper
or other conductive material, and its thickness is 50 to 100 .mu.m.
It should be noted that a metal film may be formed on the surface
of the lead 20 at its end by means of electroplating, etc., in
order to facilitate connection of the lead 20 to an electrode pad,
etc. Also on the surface of the lead 20 in the location
corresponding to the front side of a seal area 31c of a package
sheet 31 mentioned later, a seal reinforcement material 21 made of
the same material as a seal layer LA3 mentioned later is provided
so as to surround this location. This seal reinforcement material
21 is formed by sandwiching the lead 20 between two sheets,
enclosing the lead 20 with one sheet, or coating a liquid on the
surface of the lead 20, among others.
[0071] Next, as shown in FIGS. 10 (A) and (B), one end of the one
lead 20 is placed over the lead connection parts 11a1, 13a1
connected earlier, and this end is directly joined, by means of
spot-welding, ultrasonic welding, clinching, etc., to connect the
lead 20 to the lead connection parts 11a1, 13a1 connected earlier
(refer to the joining location WP2). Also, one end of the other
lead 20 is placed over the lead connection parts 12a1 connected
earlier, and this end is directly joined, by means of spot-welding,
ultrasonic welding, clinching, etc., to connect the lead 20 to the
lead connection parts 12a1 connected earlier (refer to the joining
location WP2).
[0072] As shown in FIG. 10 (A), by making each lead 20 smaller than
the lead connection parts 11a1, 12a1, 13a1 in the lateral dimension
and by ensuring the joining location WP2 is positioned inside the
joining locations WP1 on the left and right and that these joining
locations WP1, WP2 lie along a straight line, problems of
connection failures caused by overlapping joining areas can be
suppressed to reliably make each connection, while the electrical
resistances between the left/right joining locations WP1 and
joining location WP2, or specifically electrical resistance between
the one lead 20 and collector electrode layers 11a, 13a and
electrical resistance between the other lead 20 and collector
electrode layer 12a, can be reduced.
[0073] Next, FIGS. 11 to 15 are used to explain the constitution
of, and method for creating, the package 30.
[0074] To create the package 30, a package sheet 31 shown in FIGS.
11 (A) to (C) is prepared. As shown in FIG. 11 (C), this package
sheet 31 is made of a three-layer laminate film constituted by a
protective layer LA1, a barrier layer LA2 and a seal layer LA3
laminated in this order. The protective layer LA1 is made of nylon,
polyethylene phthalate or other heat-resistant plastic, and its
thickness is 10 to 50 .mu.m. The barrier layer LA2 is made of
aluminum or other metal or metal oxide, and its thickness is 10 to
50 .mu.m. The seal layer LA3 is made of polypropylene, modified
polypropylene or other thermoplastic, and its thickness is 30 to 50
.mu.m.
[0075] As shown in FIGS. 11 (A) and (B), the package sheet 31 forms
a rectangular shape of specified longitudinal dimension L31 and
lateral dimension W31, and has a rectangular solid overhang 31a on
the right side of the center in the longitudinal direction, and
provided inside of this overhang is a concaved part 31b of similar
shape. The depth of the concaved part 31b is slightly larger than
the vertical dimension (overall thickness) of the aforementioned
capacitor element 10, and its outline in top view is slightly
larger than the outline of the capacitor element 10 in top view.
The area of the package sheet 31 on the right side of the center in
the longitudinal direction where this concaved part 31b does not
exist is a seal area 31c, and the seal layer LA3 is positioned on
the top surface of the package sheet 31.
[0076] To create the package 30 (refer to FIGS. 1 (A) to (C)), as
shown in FIG. 12 the capacitor element 10 of the capacitor element
10 with lead 20 as shown in FIG. 10 (A) is inserted into the
concaved part 31b, and at the same time the seal reinforcement
material 21 of each lead 20 is placed on the front side of the seal
area 31c. Since the longitudinal dimension of each seal
reinforcement material 21 is slightly larger than the longitudinal
dimension of the front side of the seal area 31c, when inserting
the capacitor element 10 into the concaved part 31b, the front edge
of each seal reinforcement material 21 is caused to project
slightly outward from the front edge of the front side of the seal
area 31c.
[0077] Next, as shown in FIG. 13, the part of the package sheet 31
in FIG. 12 on the left side of the center in the longitudinal
direction is folded upward along the reference line VSL shown in
the drawing, and the left side is superposed with the right
side.
[0078] This way, a semi-finished package (no reference numeral) is
obtained, which has a configuration in which the seal layer LA3 on
the left side of the package sheet 31 is facing the seal layer LA3
in the seal area 31c on the right side.
[0079] Next, as shown in FIG. 14, the semi-finished package shown
in FIG. 13 is flipped upside down and heat is applied to the left
side and right side to heat-seal the mutually facing seal layers
LA3, after which the heat-sealed left side and right side are
folded upward and then heat is applied again to a folded part 31d
to increase the reliability of heat-sealing (refer to the
heat-sealing location HS).
[0080] Next, as shown in FIG. 15, electrolyte ES (such as a mixture
of propylene carbonate (solvent) and triethyl methyl ammonium
fluoroborate (solute)) is injected into the concaved part 31b using
an appropriate injection implement through the front side of the
semi-finished package in FIG. 14 which is not yet heat-sealed.
After the electrolyte has been injected, heat is applied to the
front side of the semi-finished package to heat-seal the mutually
facing seal layers LA3 by sandwiching each seal reinforcement
material 21 in between (refer to the heat-sealing location HS).
[0081] This way, an electric double-layer capacitor structured in
such a way that the capacitor element 10 is sealed in the package
30 together with electrolyte ES (refer to FIGS. 1 (A) to (C)) can
be obtained.
[0082] It should be noted that the seal layer LA3 of the package
sheet 31 is not itself significantly thick, so the lead 20 may
contact the barrier layer LA2 depending on the melting condition
when the front side of the semi-finished package is
heat-sealed.
[0083] However, heat-sealing the front side of the semi-finished
package by sandwiching each seal reinforcement material 21 in
between allows the virtual thickness of the seal layer LA3 to be
increased by the thickness of each seal reinforcement material 21,
as a result of which contact between each lead 20 and the barrier
layer LA2 can be prevented in a reliable manner at the time of
heat-sealing.
[0084] The capacitor element 10 of the aforementioned electric
double-layer capacitor has a configuration in which the laminate
shown in FIG. 7 (A) is folded along the reference line VSL and
superposed (refer to FIG. 9 (B)), where the collector electrode
layer 11a and polarizable electrode layer 11b of the first
electrode sheet 11, the collector electrode layer 12a and each
polarizable electrode layer 12b of the second electrode sheet 12,
the collector electrode layer 13a and polarizable electrode layer
13b of the third electrode sheet 13, and two separation sheets 14,
are connected to each other via the folded locations. Accordingly,
although the layer structure in section view is the same as that of
the conventional capacitor element, this capacitor element can have
fewer edge areas in the polarizable electrode layers 11b, 12b, 13b
compared to the conventional capacitor element.
[0085] In other words, the conventional capacitor element is
vulnerable to breakage and other damage due to a higher density of
lines of electric force at the edges of each polarizable electrode
layer when voltage is applied to the capacitor element, and
therefore presents the risk of problems affecting the capacitor
element as a whole, such as a drop in its voltage resistance
characteristics and shortening of its life caused by such damage.
On the other hand, the aforementioned capacitor element 10 has
fewer edge areas in each polarizable electrode layer 11b, 12b or
13b compared to the conventional capacitor element and can
therefore effectively suppress the aforementioned damage and
reliably suppress problems affecting the capacitor element 10 as a
whole, such as drop in its voltage resistance characteristics and
shortening of its life caused by such damage.
[0086] Also, with respect to the capacitor element 10 of the
aforementioned electric double-layer capacitor, it can be
considered that the collector electrode layer, polarizable
electrode layer, separation sheet, polarizable electrode layer and
collector electrode layer constitute one charge/discharge cell, and
therefore given the layer structure shown in FIG. 9 (C), this
capacitor element 10 appears to have four charge/discharge cells.
However, the capacitor element 10 is folded in the manner shown in
FIG. 9 (B) and the collector electrode layer 11a and polarizable
electrode layer 11b of the first electrode sheet 11, collector
electrode layer 12a and each polarizable electrode layer 12b of the
second electrode sheet 12, collector electrode layer 13a and
polarizable electrode layer 13b of the third electrode sheet 13,
and two separation sheets 14, are connected to each other via the
folded locations, and accordingly the capacitor element 10 can be
expressed by an equivalent circuit where two charge/discharge cells
are electrically connected in parallel with a pair of leads 20.
[0087] In other words, although the layer structure in section view
is the same as that of the conventional capacitor element, the
number of charge/discharge cells can be reduced by half, meaning
that the number of charge/discharge cells can be reduced to limit
the range of variation in charge/discharge characteristics. As a
result, undesirable effects of varying charge/discharge
characteristics, or specifically accumulation of physicochemical
damage of certain charge/discharge cells that offer good
charge/discharge characteristics and therefore perform more
charging/discharging than other cells, where such damage causes the
charge/discharge characteristics of the capacitor element as a
whole to drop, makes the life of the capacitor element shorter, or
presents other problems, can be suppressed in a reliable
manner.
[0088] Furthermore, the capacitor element 10 of the aforementioned
electric double-layer capacitor is not only folded in the manner
shown in FIG. 9 (B), but it is also such that the lead connection
parts 11a1 of the first electrode sheet 11 and lead connection
parts 13a1 of the third electrode sheet 13 are interconnected,
while the lead connection parts 12a1 of the second electrode sheet
12 are interconnected.
[0089] In other words, the polarizable electrode layer 11b of the
first electrode sheet 11 positioned at the outermost point of the
capacitor element 10 is contacting the separation sheet 14 present
on its inside, while this separation sheet 14 is contacting the one
polarizable electrode layer 12b of the second electrode sheet 12
and the other polarizable electrode layer 12b of the second
electrode sheet 12 is contacting the separation sheet 14 present on
its inside, while this separation sheet 14 is contacting the
polarizable electrode layer 13b of the third electrode sheet 13,
and the foregoing arrangement has the effect that, by
interconnecting the lead connection parts 11a1 of the first
electrode sheet 11 and lead connection parts 13a1 of the third
electrode sheet 13, and also by interconnecting the lead connection
parts 12a1 of the second electrode sheet 12, the relative positions
of the first electrode sheet 11, second electrode sheet 12, third
electrode sheet 13 and each separation sheet 14 constituting the
capacitor element 10 can be fixed properly in the longitudinal
direction and lateral direction.
[0090] In other words, the first electrode sheet 11, second
electrode sheet 12, third electrode sheet 13 and two separation
sheets 14 constituting the capacitor element 10 are not easily
displaced relative to each other, which has the effect of reliably
suppressing deformation of the shape of the capacitor element 10
due to the aforementioned displacement, and consequent
deterioration of the charge/discharge characteristics of the
element, in the process of manufacturing the electric double-layer
capacitor, the process of using the manufactured electric
double-layer capacitor, or the like.
[0091] FIGS. 16 (A) and (B) show examples of anti-displacement
projections provided on at least one of the first electrode sheet
11 and third electrode sheet 13, and on the second electrode sheet
12, respectively.
[0092] In the case of the capacitor element 10-1 shown in FIG. 16
(A), an anti-displacement projection 11a2, whose height is greater
than the thickness of the polarizable electrode layer 11b, is
provided on the outer periphery of the collector electrode layer
11a of the first electrode sheet 11, an anti-displacement
projection 12a2, whose height is greater than the thickness of the
polarizable electrode layer 12b, is provided on the outer periphery
of the collector electrode layer 12a of the second electrode sheet
12, and an anti-displacement projection 13a2, whose height is
greater than the thickness of the polarizable electrode layer 13b,
is provided on the outer periphery of the collector electrode layer
13a of the third electrode sheet 13. These anti-displacement
projections 11a2, 12a2, 13a2 may be shaped in such a way that they
are connected or not connected along the outer peripheries, but it
is desirable that they are provided in at least two locations of
the outer periphery in order to prevent two-dimensional
displacement.
[0093] As shown by this drawing, the anti-displacement projection
11a2 of the first electrode sheet 11 bites into the adjacent
separation sheet 14 without piercing through it, the
anti-displacement projection 12a2 of the second electrode sheet 12
bites into the adjacent separation sheet 14 without piercing
through it, and the anti-displacement projection 13a2 of the third
electrode sheet 13 bites into the adjacent separation sheet 14
without piercing through it. In the drawing, the anti-displacement
projections 12a2, 13a2 bite into the separation sheets 14 in the
second and third layers from the top in a manner facing each other
in the vertical direction, but contact between the
anti-displacement projections 12a2, 13a2 can be avoided by
adjusting their biting depths.
[0094] In the case of the capacitor element 10-2 shown in FIG. 16
(B), an anti-displacement projection 11a2, whose height is greater
than the thickness of the polarizable electrode layer 11b, is
provided on the outer periphery of the collector electrode layer
11a of the first electrode sheet 11, and an anti-displacement
projection 12a2, whose height is greater than the thickness of the
polarizable electrode layer 12b, is provided on the outer periphery
of the collector electrode layer 12a of the second electrode sheet
12, but no anti-displacement projection is provided on the
collector electrode layer 13a of the third electrode sheet 13.
These anti-displacement projections 11a2, 12a2 may be shaped in
such a way that they are connected or not connected along the outer
peripheries, but it is desirable that they are provided in at least
two locations of the outer periphery in order to prevent
two-dimensional displacement.
[0095] As shown by this drawing, the anti-displacement projection
11a2 of the first electrode sheet 11 bites into the adjacent
separation sheet 14 without piercing through it, while the
anti-displacement projection 12a2 of the second electrode sheet 12
bites into the adjacent separation sheet 14 without piercing
through it, and the anti-displacement projection 13a2 of the third
electrode sheet 13 bites into the adjacent separation sheet 14
without piercing through it. No anti-displacement projection is
provided on the collector electrode layer 13a of the third
electrode sheet 13 because, as explained earlier, the relative
positions of the collector electrode layer 11a of the first
electrode sheet 11 and collector electrode layer 13a of the third
electrode sheet 13 are fixed in the longitudinal direction and
lateral direction by means of interconnection of the lead
connection parts 11a1, 13a1.
[0096] Methods that can be adopted to form the aforementioned
anti-displacement projections 11a2, 12a2, 13a2 include a method to
press an appropriate processing jig against the outer peripheries
of the collector electrode layers 11a, 12a, 13a to deform the outer
peripheries, and a method to use a press cutter to cause the outer
peripheries of the collector electrode layers 11a, 12a, 13a to sag
by means of press cutting when cutting along the virtual lines PL1
to PL3 in the creation method explained in FIGS. 6 (A) to (C).
[0097] By adopting the projection biting structure shown in FIGS.
16 (A) and (B), mutual displacement of the first electrode sheet
11, second electrode sheet 12, third electrode sheet 13 and two
separation sheets 14 constituting the capacitor element 10-1 or
10-2 can be prevented in a more reliable manner, which suppresses,
in a more reliable manner, deformation of the shape of the
capacitor element 10-1 or 10-2 due to the aforementioned
displacement, and consequent deterioration of the charge/discharge
characteristics of the element, in the process of manufacturing the
electric double-layer capacitor, the process of using the
manufactured electric double-layer capacitor, or the like.
[0098] Orientations of the aforementioned anti-displacement
projections are not limited to those shown in FIGS. 16 (A) and (B)
and, for example, one of the anti-displacement projections 12a2
provided in the lateral direction on the collector electrode layer
12a of the second electrode sheet 12 may be facing downward, while
the other projection in the lateral direction may be facing upward.
Or, one of the anti-displacement projections 13a2 provided in the
lateral direction on the collector electrode layer 13a of the third
electrode sheet 13 may be facing downward, while the other
projection in the lateral direction may be facing upward, and the
downward-facing anti-displacement projection 13a2 may be caused to
bite into the opposing collector electrode layer 13a.
Second Embodiment
[0099] FIGS. 17 to 30 show an embodiment where the present
invention is applied to a lithium ion capacitor. This lithium ion
capacitor has a capacitor element 40, a pair of leads 20 connected
to the capacitor element 40, and a package 50 in which the
capacitor element 40 is sealed in a manner partially exposing the
pair of leads 20.
[0100] Note that, in the following explanations, the direction
toward the viewer, away from the viewer, right, left, bottom and
top in FIG. 17 (A) are referred to as top, bottom, front, rear,
left and right, respectively, while the corresponding directions in
other drawings are also referred to as top, bottom, front, rear,
left and right, respectively, for the convenience of explanation.
Also note that the constitutions of the lead 20 and seal
reinforcement material 21 are the same as those described in the
first embodiment and therefore explained using the same reference
numerals.
[0101] First, FIGS. 18 to 25 are used to explain the constitution
of, and method for creating, the capacitor element 40.
[0102] To create the capacitor element 40, a first electrode sheet
41 shown in FIGS. 18 (A) and (B), a second electrode sheet 42 shown
in FIGS. 19 (A) and (B), and a separation sheet 43 shown in FIGS.
20 (A) and (B) are prepared.
[0103] As shown in FIGS. 18 (A) and (B), the first electrode sheet
41 has a rectangular collector electrode layer 41a of specified
longitudinal dimension L41 and lateral dimension W41, as well as a
polarizable electrode layer 41b formed over the entire top surface
of the collector electrode layer 41a, except for both ends in the
longitudinal direction, by means of coating, etc. The longitudinal
dimension L41b of this polarizable electrode layer 41a is slightly
smaller than the aforementioned longitudinal dimension L41. The
collector electrode layer 41a is made of copper or other conductive
material, and its thickness is 5 to 50 .mu.m. The polarizable
electrode layer 41b is made of graphite or other substance that can
reversibly support lithium ions, and its thickness is 50 to 100
.mu.m. Also, a rectangular lead connection part 41a1 is provided on
the right side of the collector electrode layer 41a on both ends in
the longitudinal direction in a manner integral with, and at the
same thickness as, the collector electrode layer 41a.
[0104] As shown in FIGS. 19 (A) and (B), the second electrode sheet
42 has a rectangular collector electrode layer 42a of longitudinal
dimension L42 slightly smaller than longitudinal dimension L41
mentioned above, and a lateral dimension W42 slightly smaller than
lateral dimension W41 mentioned above, as well as a polarizable
electrode layer 42b formed over the entire bottom surface of the
collector electrode layer 42a by means of coating, etc. It should
be noted that the difference between the longitudinal dimension L42
of the collector electrode layer 42a and aforementioned
longitudinal dimension L41, and the difference between the lateral
dimension W42 and aforementioned lateral dimension W41, are
actually approx. 0.3 to 2.0 mm. The collector electrode layer 42a
is made of aluminum or other conductive material, and its thickness
is 5 to 100 .mu.m. The polarizable electrode layer 42b is made of
active carbon or other substance that can reversibly support
lithium ions, and its thickness is 5 to 200 .mu.m. Also, a
rectangular lead connection part 42a1, whose lateral dimension
(width) is smaller and whose longitudinal dimension is greater than
those of the aforementioned lead connection part 41a1, is provided
on the left side of the collector electrode layer 42a on both ends
in the longitudinal direction in a manner integral with, and at the
same thickness as, the collector electrode layer 42a. The distance
between the front edge of the front lead connection part 42a1 and
the rear edge of the rear lead connection part 42a1 is the same as
the distance between the front edge of the front lead connection
part 41a1 and the rear edge of the rear lead connection part 41a1
of the aforementioned first electrode sheet 41.
[0105] In other words, the shape in top view of the collector
electrode layer 41a (excluding the lead connection part 41a1) of
the first electrode sheet 41 is larger than the shape in top view
of the collector electrode layer 42a (excluding the lead connection
part 42a1) of the second electrode sheet 42. Also, the shape in top
view of the polarizable electrode layer 41b of the first electrode
sheet 41 is larger than the shape in top view of the polarizable
electrode layer 42b of the second electrode sheet 42.
[0106] Furthermore, the collector electrode layer 41a (including
the lead connection part 41a1) and polarizable electrode layer 41b
of the first electrode sheet 41 are linearly symmetrical over the
reference line VSL running at the center in the longitudinal
direction as shown in FIG. 18 (A). The collector electrode layer
42a (including the lead connection part 42a1) and the polarizable
electrode layer 42b of the second electrode sheet 42 are linearly
symmetrical over the reference line VSL running at the center in
the longitudinal direction as shown in FIG. 19 (A).
[0107] As shown in FIGS. 20 (A) and (B), the separation sheet 43
has a rectangular shape of longitudinal dimension L43 slightly
larger than longitudinal dimension L41 mentioned above, and a
lateral dimension W43 slightly larger than lateral dimension W41
mentioned above. The separation sheet 43 is made of cellulose
sheet, plastic sheet or other ion permeation sheet, and its
thickness is approx. 10 to 50 .mu.m.
[0108] The aforementioned first electrode sheet 41, second
electrode sheet 42 and separation sheet 43 can be obtained easily
by cutting material sheets BS11 to BS13 along virtual lines PL11 to
PL13 and then punching out the insides, respectively, as shown in
FIGS. 21 (A) to (C). As shown by the drawings, the material sheet
BS11 for first electrode sheet 41 is a strip-shaped collector
electrode layer with a strip-shaped polarizable electrode layer
formed on its top surface, while the material sheet BS12 for second
electrode sheet 42 is a strip-shaped collector electrode layer with
a strip-shaped polarizable electrode layer formed on its top
surface.
[0109] To create the capacitor element 40 (refer to FIGS. 24 (A)
and 17 (A)), the prepared first electrode sheet 41, second
electrode sheet 42 and separation sheet 43 are stacked in such a
way that they are ordered as first electrode sheet 41, separation
sheet 43 and second electrode sheet 42 from the bottom, as shown in
FIGS. 22 (A) and (B).
[0110] When stacking the sheets, the outer periphery of the
polarizable electrode layer 41b of the first electrode sheet 41 is
caused to project outward from the outer periphery of the
polarizable electrode layer 42b of the second electrode sheet 42,
while the outer periphery of the separation sheet 43 is caused to
project outward from the outer periphery of the collector electrode
layer 41a of the first electrode sheet 41. Also, the lead
connection parts 41a1, 42a1 of the first electrode sheet 41 and
second electrode sheet 42 are caused to project by the same length
from the separation sheet 43.
[0111] This way, a laminate (no reference numeral) is obtained
where the polarizable electrode layer 41b of the first electrode
sheet 41 and the polarizable electrode layer 42b of the second
electrode sheet 42 are contacting the separation sheet 43.
[0112] Next, as shown in FIGS. 23 (A) and (B), the part of the
laminate in FIG. 22 (A) on the left side of the center in the
longitudinal direction is folded upward along the reference line
VSL shown in the drawing, and the left side is superposed with the
right side.
[0113] At the time of this superposition, the outer peripheries of
the lead connection parts 41a1 of the first electrode sheet 41 are
caused to align in the superposing direction, while the outer
peripheries of the lead connection parts 42a1 of the second
electrode sheet 42 are caused to align in the superposing
direction.
[0114] This way, a folded laminate (no reference numeral) is
obtained, which has a configuration in which the first electrode
sheet 41, second electrode sheet 42 and separation sheet 43 are
folded into two at an angle of approx. 180 degrees over the
reference line VSL in such a way that the lead connection parts
41a1 of the first electrode sheet 41 are facing each other and the
lead connection parts 42a1 of the second electrode sheet 42 are
facing each other.
[0115] The next step in this folded laminate shown in FIG. 23 (A)
is that, as shown in FIGS. 24 (A) to (C) the mutually facing lead
connection parts 41a1 of the first electrode sheet 41 are
superposed and two locations on both sides in the lateral direction
are directly joined by means of spot-welding, ultrasonic welding,
clinching, etc., with the separation sheet 43 in between, to
interconnect the lead connection parts 41a1 (refer to the joining
location WP11). Also, the mutually facing lead connection parts
42a1 of the second electrode sheet 42 are superposed at positions
not contacting the aforementioned lead connection parts 41a1, and
two locations on both sides in the lateral direction are directly
joined by means of spot-welding, ultrasonic welding, clinching,
etc., with the separation sheet 43 in between, to interconnect the
lead connection parts 42a1 (refer to the joining location
WP11).
[0116] Next, as shown in FIG. 24 (A), a lithium sheet 44 for
lithium doping is attached, by means of pressure bonding, etc.,
onto the top surface of the collector electrode layer 41a of the
first electrode sheet 41.
[0117] This way, the capacitor element 40 is obtained, which has a
configuration in which the first electrode sheet 41, second
electrode sheet 42 and separation sheet 43 are folded into two at
an angle of approx. 180 degrees over the reference line VSL, while
the lead connection parts 41a1 of the first electrode sheet 41 are
interconnected, and the lead connection parts 42a1 of the second
electrode sheet 42 are interconnected.
[0118] It should be noted that in FIGS. 18 to 24 (and also in FIG.
25), the thickness of the collector electrode layer 41a and
polarizable electrode layer 41b of the first electrode sheet 41,
the thickness of the collector electrode layer 42a and polarizable
electrode layer 42b of the second electrode sheet 42, and the
thickness of the separation sheet 43, have been increased from
their actual thicknesses for the convenience of illustration, and
therefore the vertical dimensions (overall thicknesses) in FIGS. 22
(B), 23 (B), 24 (B) and 24 (C) appear thicker than they actually
are.
[0119] However, the thickness of the collector electrode layer 41a
and polarizable electrode layer 41b of the first electrode sheet
41, the thickness of the collector electrode layer 42a and each
polarizable electrode layer 42b of the second electrode sheet 42,
and the thickness of the separation sheet 43, are in a range of 5
to 200 .mu.m and therefore even when the average of all layers is
assumed as 60 .mu.m, for example, the actual vertical dimension
(overall thickness) in FIG. 22 (B) becomes 300 .mu.m, while the
actual vertical dimension (overall thickness) in FIGS. 23 (B), 24
(B) and 24 (C) becomes 600 .mu.m.
[0120] In other words, the actual vertical dimension (overall
thickness) of the capacitor element 40 shown in FIG. 24 (A) is less
than 1000 .mu.m, meaning that, with the folded laminate in FIG. 24
(B), the radius of curvature of the outer surface at the folded
location is much smaller than illustrated and consequently the lead
connection parts 41a1, 42a1 are virtually not displaced in the
longitudinal direction when folded. In addition, the polarizable
electrode layers 41b, 42b do not separate from the collector
electrode layers 41a, 42a when the laminate is folded, and the
polarizable electrode layers 41b, 42b do not lose contact with the
separation sheet 43, either. Furthermore, the collector electrode
layers 41a, 42a, polarizable electrode layers 41b, 42b and
separation sheet 43 have enough flexibility to permit folding and
thus do not break at the folded locations.
[0121] Also in FIG. 24 (B), the lead connection parts are partially
extended for the convenience of illustration, or specifically to
explain the connection of lead connection parts 41a1 and connection
of lead connection parts 42a1 on the folded laminate. As understood
from the foregoing explanation, however, in reality the lead
connection parts can be connected without such extensions.
[0122] Next, FIG. 25 is used to explain the constitution of the
lead 20 and how it is connected to the capacitor element 40.
[0123] To connect the lead 20 to the capacitor element 40, the lead
20 shown in FIGS. 25 (A) and (B) is prepared. This lead 20 is
formed into a short strip shape made of aluminum, platinum, copper
or other conductive material, and its thickness is 50 to 100 .mu.m.
It should be noted that a metal film may be formed on the surface
of the lead 20 at its end by means of electroplating, etc., in
order to facilitate connection of the lead 20 to an electrode pad,
etc. Also on the surface of the lead 20 in the location
corresponding to the front side of a seal area 51c of a package
sheet 51 mentioned later, a seal reinforcement material 21 made of
the same material as a seal layer LA3 mentioned later is provided
so as to surround this location. This seal reinforcement material
21 is formed by sandwiching the lead 20 between two sheets,
enclosing the lead 20 with one sheet, or coating a liquid on the
surface of the lead 20, among others.
[0124] Next, as shown in FIGS. 25 (A) and (B), one end of the lead
20 is placed over the lead connection parts 41a1 connected earlier,
at the location projecting from the separation sheet 43, and this
end is directly joined, by means of spot-welding, ultrasonic
welding, clinching, etc., to connect the lead 20 to the lead
connection parts 41a1 connected earlier (refer to the joining
location WP12). Also, one end of the other lead 20 is placed over
the lead connection parts 42a1 connected earlier, at the location
projecting from the separation sheet 43, and this end is directly
joined, by means of spot-welding, ultrasonic welding, clinching,
etc., to connect the lead to the lead connection parts 42a1
connected earlier (refer to the joining location WP12).
[0125] Next, FIGS. 26 to 30 are used to explain the constitution
of, and method for creating, the package 50.
[0126] To create the package 50, a package sheet 51 shown in FIGS.
26 (A) to (C) is prepared. As shown in FIG. 26 (C), this package
sheet 51 is made of a three-layer laminate film constituted by a
protective layer LA1, a barrier layer LA2 and a seal layer LA3
laminated in this order. The protective layer LA1 is made of nylon,
polyethylene phthalate or other heat-resistant plastic, and its
thickness is 10 to 50 .mu.m. The barrier layer LA2 is made of
aluminum or other metal or metal oxide, and its thickness is 10 to
50 .mu.m. The seal layer LA3 is made of polypropylene, modified
polypropylene or other thermoplastic, and its thickness is 30 to 50
.mu.m.
[0127] As shown in FIGS. 26 (A) and (B), the package sheet 51 forms
a rectangular shape of specified longitudinal dimension L51 and
lateral dimension W51, and has a rectangular solid overhang 51a on
the right side of the center in the longitudinal direction, and
provided inside of this overhang is a concaved part 51b of similar
shape. The depth of the concaved part 51b is slightly larger than
the vertical dimension (overall thickness) of the aforementioned
capacitor element 40, and its outline in top view is slightly
larger than the outline of the capacitor element 40 in top view.
The area of the package sheet 51 on the right side of the center in
the longitudinal direction where this concaved part 51b does not
exist is a seal area 51c, and the seal layer LA3 is positioned on
the top surface of the package sheet 51.
[0128] To create the package 50 (refer to FIGS. 17 (A) to (C)), as
shown in FIG. 27 the capacitor element 40 of the capacitor element
40 with lead 20 as shown in FIG. 25 (A) is inserted into the
concaved part 51b, and at the same time the seal reinforcement
material 21 of each lead 20 is placed on the front side of the seal
area 51c. Since the longitudinal dimension of each seal
reinforcement material 21 is slightly larger than the longitudinal
dimension of the front side of the seal area 51c, when inserting
the capacitor element 40 into the concaved part 51b, the front edge
of each seal reinforcement material 21 is caused to project
slightly outward from the front edge of the front side of the seal
area 51c.
[0129] Next, as shown in FIG. 28, the part of the package sheet 51
in FIG. 27 on the left side of the center in the longitudinal
direction is folded upward along the reference line VSL shown in
the drawing, and the left side is superposed with the right
side.
[0130] This way, a semi-finished package (no reference numeral) is
obtained, which has a configuration in which the seal layer LA3 on
the left side of the package sheet 51 is facing the seal layer LA3
in the seal area 51c on the right side.
[0131] Next, as shown in FIG. 29, the semi-finished package shown
in FIG. 28 is flipped upside down and heat is applied to the right
side to heat-seal the mutually facing seal layers LA3, after which
heat is applied to the front side to heat-seal the mutually facing
seal layers LA3 by sandwiching each seal reinforcement material 21
in between (refer to the heat-sealing location HS).
[0132] Next, as shown in FIG. 30, electrolyte ES (such as a mixture
of propylene carbonate (solvent) and lithium hexafluorophosphate
(solute)) is injected into the concaved part 51b using an
appropriate injection implement through the left side of the
semi-finished package in FIG. 29 which is not yet heat-sealed.
After the electrolyte has been injected, heat is applied to the
left side of the seal area 51c to heat-seal the mutually facing
seal layers LA3 (refer to the heat-sealing location HS).
[0133] This way, a lithium ion capacitor structured in such a way
that the capacitor element 40 is sealed in the package 50 together
with electrolyte ES (refer to FIGS. 17 (A) to (C)) can be
obtained.
[0134] It should be noted that the seal layer LA3 of the package
sheet 51 is not itself significantly thick, so the lead 20 may
contact the barrier layer LA2 depending on the melting condition
when the front side of the semi-finished package is
heat-sealed.
[0135] However, heat-sealing the front side of the semi-finished
package by sandwiching each seal reinforcement material 21 in
between allows the virtual thickness of the seal layer LA3 to be
increased by the thickness of each seal reinforcement material 21,
as a result of which contact between each lead 20 and the barrier
layer LA2 can be prevented in a reliable manner at the time of
heat-sealing.
[0136] The capacitor element 40 of the aforementioned lithium ion
capacitor has a configuration in which the laminate shown in FIG.
22 (A) is folded along the reference line VSL and superposed (refer
to FIG. 24 (B)), where the collector electrode layer 41a and
polarizable electrode layer 41b of the first electrode sheet 41,
the collector electrode layer 42a and polarizable electrode layer
42b of the second electrode sheet 42 and the separation sheet 43,
are connected to each other via the folded locations. Accordingly,
although the layer structure in section view is the same as that of
the conventional capacitor element, this capacitor element can have
fewer edge areas in the polarizable electrode layers 41b, 42b
compared to the conventional capacitor element.
[0137] In other words, the conventional capacitor element is
vulnerable to breakage and other damage due to higher density of
lines of electric force at the edges of each polarizable electrode
layer when voltage is applied to the capacitor element, and
therefore presents the risk of problems affecting the capacitor
element as a whole, such as a drop in its voltage resistance
characteristics and shortening of its life caused by the damage. On
the other hand, the aforementioned capacitor element 40 has fewer
edge areas in each polarizable electrode layer 41b, 42b compared to
the conventional capacitor element and can therefore effectively
suppress the aforementioned damage and reliably suppress problems
affecting the capacitor element 40 as a whole, such as a drop in
its voltage resistance characteristics and shortening of its life
caused by such damage.
[0138] Also, with respect to the capacitor element 40 of the
aforementioned lithium ion capacitor, it can be considered that the
collector electrode layer, polarizable electrode layer, separation
sheet, polarizable electrode layer and collector electrode layer
constitute one charge/discharge cell, and therefore given the layer
structure shown in FIG. 24 (C), this capacitor element 40 appears
to have two charge/discharge cells. However, the capacitor element
40 is folded in the manner shown in FIG. 24 (B) and the collector
electrode layer 41a and polarizable electrode layer 41b of the
first electrode sheet 41, the collector electrode layer 42a and
polarizable electrode layer 42b of the second electrode sheet 42
and the separation sheet 43 are connected to each other via the
folded locations, and accordingly the capacitor element 40 can be
expressed by an equivalent circuit where one charge/discharge cell
is electrically connected with a pair of leads 20.
[0139] In other words, although the layer structure in section view
is the same as that of the conventional capacitor element, the
number of charge/discharge cells can be reduced by half, meaning
that the number of charge/discharge cells can be reduced to limit
the range of variation in charge/discharge characteristics. As a
result, undesirable effects of varying charge/discharge
characteristics, or specifically accumulation of physicochemical
damage on certain charge/discharge cells that offer good
charge/discharge characteristics and therefore perform more
charging/discharging than other cells, where such damage causes the
charge/discharge characteristics of the capacitor element as a
whole to drop, makes the life of the capacitor element shorter, or
presents other problems, can be suppressed in a reliable
manner.
[0140] Furthermore, the capacitor element 40 of the aforementioned
lithium ion capacitor is not only folded in the manner shown in
FIG. 24 (B), but it is also such that the lead connection parts
41a1 of the first electrode sheet 41 are interconnected via the
separation sheet 43, while the lead connection parts 42a1 of the
second electrode sheet 42 are interconnected via the separation
sheet 43.
[0141] In other words, the polarizable electrode layer 41b of the
first electrode sheet 41 positioned at the outermost point of the
capacitor element 40 is contacting the separation sheet 43 present
on its inside, while this separation sheet 43 is contacting the
polarizable electrode layer 42b of the second electrode sheet 42,
and the foregoing arrangement has the effect that, by
interconnecting the lead connection parts 41a1 of the first
electrode sheet 41 via the separation sheet 43, and also by
interconnecting the lead connection parts 42a1 of the second
electrode sheet 42 via the separation sheet 43, the relative
positions of the first electrode sheet 41, the second electrode
sheet 42 and the separation sheet 43 constituting the capacitor
element 40 can be fixed properly in the longitudinal direction and
lateral direction.
[0142] In other words, the first electrode sheet 41, second
electrode sheet 42 and separation sheet 43 constituting the
capacitor element 40 are not easily displaced relative to each
other, which has the effect of reliably suppressing deformation of
the shape of the capacitor element 40 due to the aforementioned
displacement, and consequent deterioration of the charge/discharge
characteristics of the element, in the process of manufacturing the
lithium ion capacitor, the process of using the manufactured
lithium ion capacitor, or the like.
[0143] Note that, while not illustrated, anti-displacement
projections similar to the anti-displacement projections 11a2,
12a2, 13a2 shown in FIGS. 16 (A) and (B) can be provided on both
the outer periphery of the collector electrode layer 41a of the
first electrode sheet 41 and the outer periphery of the collector
electrode layer 42a of the second electrode sheet 42, or only on
the outer periphery of the collector electrode layer 41a of the
first electrode sheet 41, to prevent relative displacement of the
first electrode sheet 41, the second electrode sheet 42 and the
separation sheet 43 in a more reliable manner, which has the effect
of more reliably suppressing deformation of the shape of the
capacitor element due to the aforementioned displacement, and
consequent deterioration of the charge/discharge characteristics of
the element, in the process of manufacturing the lithium ion
capacitor, the process of using the manufactured lithium ion
capacitor, or the like.
Other Embodiments
[0144] (1) The first embodiment shows constituting the capacitor
element 10 by folding and superposing the laminate made by stacking
the first electrode sheet 11, separation sheet 14, second electrode
sheet 12, separation sheet 14 and third electrode sheet 13 in this
order, while the second embodiment shows constituting the capacitor
element 10 by folding and superposing the laminate made by stacking
the first electrode sheet 41, separation sheet 43 and second
electrode sheet 42 in this order, but the number of sheets
constituting the laminate before folding may be increased from the
number of sheets constituting the laminate shown in the first
embodiment (refer to FIG. 7 (B)).
[0145] For example, the first electrode sheet 11, the separation
sheet 14, the second electrode sheet 12, the separation sheet 14,
the electrode sheet identical to the second electrode sheet 12
except that the positions of its lead connection parts 12a1 are
changed to the positions of lead connection parts 11a1 of the first
electrode sheet 11, the separation sheet 14, and the electrode
sheet identical to the third electrode sheet 13 except that the
positions of its lead connection parts 13a1 are changed to the
positions of lead connection parts 12a1 of the second electrode
sheet 12, can be stacked in this order and folded and superposed to
constitute a capacitor element having three charge/discharge cells,
and this capacitor element can still provide operation and effects
similar to the those mentioned above.
[0146] (2) An electric double-layer capacitor to which the present
invention is applied is shown in the first embodiment, while a
lithium ion capacitor to which the present invention is applied is
shown in the second embodiment, but the present invention can also
be applied to any other electrochemical device having a capacitor
element of roughly the same structure, such as a redox capacitor or
lithium ion battery, and still provide operation and effects
similar to the those mentioned above.
DESCRIPTION OF THE SYMBOLS
[0147] 10, 10-1, 10-2--Capacitor element, 11--First electrode
sheet, 11a--Collector electrode layer, 11a1--Lead connection part,
11a2--Anti-displacement projection, 11b--Polarizable electrode
layer, 12--Second electrode sheet, 12a--Collector electrode layer,
12a1--Lead connection part, 12a2--Anti-displacement projection,
12b--Polarizable electrode layer, 13--Third electrode sheet,
13a--Collector electrode layer, 13a1--Lead connection part,
13a2--Anti-displacement projection, 13b--Polarizable electrode
layer, 14--Separation sheet, WP1--Joining location, 20--Lead,
21--Seal reinforcement material, WP2--Joining location, 31--Package
sheet, 31a--Overhang, 31b--Concaved part, 31c--Seal area,
31d--Folded part, HS--Heat-sealing location, ES--Electrolyte,
40--Capacitor element, 41--First electrode sheet, 41a--Collector
electrode layer, 41a1--Lead connection part, 41b--Polarizable
electrode layer, 42--Second electrode sheet, 42a--Collector
electrode layer, 42a1--Lead connection part, 42b--Polarizable
electrode layer, 43--Separation sheet, WP11--Joining location,
WP12--Joining location, 51--Package sheet, 51a--Overhang,
51b--Concaved part, 51c--Seal area.
* * * * *